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Parkinson's Makes for Distrust, Risk Taking

Wednesday September 25, 2013

John Gever

MedPage Today - Compared with healthy controls, patients with Parkinson's disease were markedly less trusting of strangers in a psychosocial experiment, even while showing greater willingness to take risks, a researcher said here.

As in earlier studies of Parkinson's disease patients, individuals with the condition and under treatment took significantly more risks in a dice game, said Andrija Javor, MD, MSc, of Linz General Hospital in Linz, Austria.

But in a different game in which participants could give money to strangers with the possibility, but no guarantee, of an even greater reward in return, the Parkinson's disease patients were significantly stingier than were healthy controls, Javor told attendees at the World Congress of Neurology.

By the metrics used in the game, patients were only half as trusting as were controls.

Javor told MedPage Today that the finding had potentially important clinical implications for two reasons. "Trust is the foundation of the patient-physician relationship," he said. And, he added, earlier studies have indicated that trust is a factor in adherence to therapy.

But Javor also noted that the study had only 40 participants (20 each of patients and controls). "This is a pilot study and we have to be cautious how we interpret these findings," he said.

In his platform presentation, Javor explained that several neurologic elements and a variety of behavior types related to trust have previously been found to be altered in Parkinson's disease. On the brain side, these include the limbic system, the basal ganglia, and the frontal cortex. On the phenotypic side, risk perception, reward anticipation, and mentalizing functions -- all of which play into the concept of trust -- are known to be disrupted.

"But trust behavior itself has not been studied," he said.

Carol J. Schramke, PhD, a clinical neuropsychologist at Allegheny General Hospital in Pittsburgh, told MedPage Today in an email that the general outlines of the findings weren't a big surprise given what was already known about the inputs to trust behavior.

But, she added, "it is a little surprising that the researchers were able to find such a dramatic effect in a fairly small group since we also know that there is a large degree of variability [among] Parkinson's disease patients."

Another neurologist, Michelle Burack, MD, PhD, of the University of Rochester in New York, said the study methods probably couldn't support sweeping generalizations about trust behaviors in the disease.

Still, she said, Parkinson's disease does often put strains on relationships that may go beyond care-giving burden. "In relationships, in marriages, factoring this data in, maybe there are some challenges that the disease itself brings to maintaining those long-term relationships [that] should be part of the conversation."

To examine in more detail how trust may be affected in the disease, he and colleagues recruited 20 patients from Linz Hospital's movement disorders clinic who had stable motor function and were receiving conventional Parkinson's disease drugs. Testing was conducted while they were in the "on" phase of treatment, during which symptoms were as well-controlled as possible. Patients with potentially confounding psychiatric diagnoses, dementia, or apathy were excluded. An equal number of neurologically healthy and approximately age-matched controls were included as well.

Mean age was about 70 and the groups were evenly divided between men and women. Patients had a mean disease duration of 39 months (SD 42), with mean UPDRS symptom severity scores of 19.85 (SD 10.59) and mean Mini-Mental State Examination scores of 28.4 (SD 1.6). The average educational attainment was 10.9 years in the patients (SD 4.0) and 11.3 in controls (SD 5.1).

Risk acceptance was tested with a betting-type dice game. The average number of risky choices made by the patients was 10, compared with about 6.5 in controls (P not reported), Javor said, indicating a substantially greater degree of risk-taking in the patients.

In the trust game, the players were given 10 euros and told that they could give any portion of it to an unknown person seen on a computer screen. Players were told that the other person would actually receive six times the amount given -- so, for example, if the player chose to give 5 euros, the other person would receive 30 euros. Then the other person (who, according to the rules, also started with 10 euros) could give any amount of money back to the player. That was the game, and each study participant played it 16 times (with real money).

The "other person" was actually a computer, not a real person, and the amount of money returned to the player was chosen randomly. Javor explained that the pictures used for the other person were carefully chosen to show no emotional expression, so as not to influence the player's evaluations of the person's trustworthiness.

Games of this sort were originally developed for behavioral economics and psychiatric research, Javor said, in order to measure trust behaviors. He and his colleagues recognized that such a game could shed light on the neuropsychiatric manifestations of Parkinson's disease.

The mean amount that Parkinson's disease patients chose to give to the other person in the experiment was about 3.5 euros, whereas controls chose to risk an average of 7 euros by the end of 16 rounds (P not reported).

Javor said the ideal next steps in the research would be to re-run the experiment with patients in the "off" as well as "on" phases of treatment, in order to separate out the effects of drug therapy, and to perform fMRI studies to identify brain regions that may be differentially activated during trust-related experiments.

Still another potential study experiment would evaluate how trustworthy Parkinson's disease patients themselves are, Javor said.

But Burack questioned how much a money-based game such as Javor's can tell about trust in other types of interactions. Moreover, she said, even at the level of trust involving money, the game may not have been a perfect test.

"Was it that [patients] didn't trust the other person with their money or just that they wanted to hold onto more of it?" Burack wondered.

Gever, J. (25 Sep. 2013). MedPage Today. Parkinson's Makes for Distrust, Risk-Taking. www.medpagetoday.com

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